I'm looking for a good reference on integral equations (i.e., an equation in which an unknown function appears under an integral sign such as the Fredholm equation). I would like something accessible but covers approaches to showing existence. Any help would be much appreciated.
You may think of this classic by Grippenberg, Londen, Staffans.
It is quite complete and also accessible compared to other books, but not an easy reading.
Here is a well written book and easy to read by A. Jerri "Introduction to Integral Equations with Applications".